Cable for production of magnetic fields



- E. w. GREENFIELD 2,393,466

CABLE FOR PRODUCTION OF MAGNETIC FIELDS I Filed NOV. 14. 1942 2 Sheets-Sheet 1 II Ila.

Jan. 22, 1946. E. w. GREENFIELD CABLE FOR PRODUCTION OF MAGNETIC FIELDS Filed Nov. 14, 1942 2 Sheets-Sheet 2 MQN II kZ ODm m4 QHEIm QCUZQE E tOhODQZOO ZQDFMI Eqmxm zosmmnzTmmaQoz t INVENTOR. EW. GREE IELD Patented Jan. 22, 1946 CABLE FOR PRODUCTION OF MAGNETIC FIELDS Eugene W. Greenfield, Hastings on Hudson, N. Y.,

assignor to Anaconda Wire and Cable Company, New York, N. Y., a corporation of Delaware Application November 14, 1942, Serial No. 465,819

8 Claims.

The present invention relates to a device for the production of magnetic fields throughout a body of water, one of the primary objects being to provide a device which will accomplish this object without the use of dual electrodes. A further object of the invention is to provide a device for the production of magnetic fields which, having a specific gravity less than that of water, will float without the use of supporting rafts or buoys.

One use to which such a field may be put is the location of submarine cables which require servicing or repair. If an extremely sensitive current detection device is connected with the cable at a point where it emerges from the water, its location may .be very closely estimated, even at a point far off shore, if a pulsing magnetic field, which may be produced by buoyant electrodes, is brought into the vicinity of the submerged cable. Obviously, the current induced in the cablewill increase as the magnetic field approaches the submerged cable. Once the approximate location of the cable has been determined grappling hooks or similar devices may be used to bring it to the surface for repairs. Y

In practical cable maintenance operations, the device of the present invention may be towed behind a vessel so that a large area may be rapidly searched. Since the distance along the length of the cable between the fault and a known point may be determined by a Wheatstone bridge, and since the cable itself may be located by moving a magnetic field in a direction which intersects the line of the cable, the use of the device of the present invention makes it possible to quickly locate the cable at a point very close to the fault without delay.

In a copending application, Serial No. 423,842, filed December 20, 1941, the inventors have disclosed a buoyant electrode designed for the production of a magnetic field within a body of water. In that application it is suggested that a pair of buoyant electrodes, which consistsessentially of a conducting element applied to a buoyant core, may be towed behind a vessel, the electrodes being energized so that there is a flow of current through the water between them. This will result in a creation of a magnetic field which may be employed for the location of submarine cables. If it becomes desirable to separate the field created by the electrodes from incidental fields which may be generated by the towing vessel the buoyant electrodes may be pulled behind the ship at a considerable distance and still be connected with a source of electrical energy by means of shielded or concentric cables which do not creat a magnetic field. By such an arrangement it is possible to create a zone several hundred feet in width and length which is subjected to a magnetic field and, is also a considerable distance from the towing vessel.

It is the primary purpose of this invention to make available a device which will efllciently create a magnetic field throughout a body of water without the disadvantages of buoyant electrodes. One specific object of this invention is to provide means for creating a magnetic field without the use of multiple electrodes, a single cable taking their place.

A further object is to establish a magnetic field without bringing the conducting material of which the electrode is formed in contact with the surrounding water. This, of course, is an advantage of the utmost importance since it eliminates the loss of metal from the electrode by electrolytic action.

Other advantages and features of the present invention, as well as its manner of operation will be apparent from the following description when read in connection with the accompanying drawings in which similar referenc numerals denote similar parts and in which:

Figure 1 is a schematic view of the magnetic lines of force created by the. flow of current through a single conductor.

Figure 2 is a view similar to Figure l of the magnetic lines of force created by the passage of electric current through two unshielded conductors.

Figure 3 is a view similar to Figure 1 illustrating the magnetic lines of force caused by the flow of current through a single semi-shielded conductor.

Figure 4 is a view similar to Figure 1 illustrating the magnetic lines of force caused by the flow of current through a pair of semi-shielded conductors.

Figure 5 is a perspective view, certain parts having been broken away to reveal the interior construction, of a cable embodying the present invention.

An explanation of the principles underlying the present invention is simplified by reference to the diagrammatic drawings, Figures 1 to 4, which represent the magnetic fields created by the flow of electric current through conductors arranged in various combinations. It is well known that iron filings, if dispersed in the vicinity of a magnetic field, will arrange themselves in patterns from which the zones of stress may be charted.

For example, Figure 1 shows the magnetic field about a single wire H carrying a direct current, the return wire being located at a very distant or theoretically infinite point. The lines of force may be represented in this case by a series of concentrically arranged circles of increasing size.

If the return conductor Ila is now arranged parallel and relatively close to the first conductor l I the pattern is changed as shown in Figure 2. In the limited space immediately between the conductors the fields reinforce each other} but at points external to the conductors they cancel one another so that the resultant magnetic field at a short distanoedromdhe pair oi conductors is practically nil. "Therefore an insu-- lated structure containing two parallel unshielded conductors would be ineffective as ,a means at generating a magnetic field because the flux from the "go conductor nullifies that of the return i u e 3, wh ch. .Q,. compa ed. wit er? lire 1 since it illustrates a single conductor wi h a ist ntt mt h aih f ec new: a l y magnetic shield partially enclosing the conduc- .Qht qes a h fi d. ec mess e a istar'te and is bulged out on the unshielded s ide of the conductor. {This eilectls still further increased it s i of academia -,e 9l. f p ovi e wit a h fil li is the, l e o W e-far plac d e e he th elh zassl ew n P e al Asthej drawlng in dicates the field from each sensa i ns eame when a l s? emj the companion wire for a considerable distanpe lln le t e e l'sti ihaahi a i ma hereateri th draw n in icti s imfi ts p i 1H teat me at is a an ni 2.. a i ta- ,A f i iw leh i a n n t ass me p a. e 1 i. Wa w ch. i wa wh n a m la conductors, are used. Stating this an:

shielded o he th 9 1?: sfi iv @33 1??? dTwi the a ta se nw uc r w h'e n "in. F r 2 it bttneeatha q d a 'e-l. .Wh e l w l FQJ F v aws an een t emes v e l e is no m anti e-l. lilie he s. show that parallel conductors t wo lnehes apart and ener te by c rv d. m ne 'l l s" e u e t. a ma iiefl hi is similar to one producedloy a pair of unshielded located one hundred inchesapart; 'In h fl siqi $1 t- 3.1 8 ii ifi a f fty old, li c ltious separa on oithe go and conductor-s. A W on; the foregoing al n s slhl etclal M shielded placed within an insuructur, so that they are notdn'contct surrounding water and "Jet produce a discussion it is apparent e a pair 0 orniuctors,

pair of wldely separated uninsula'ted conductors immersed in water. Therefore it becomes possible to des ign a single buoyant cable'fwhich have the important advantages of compactwith a separation of several" inches. 'Arranged be'tween'tne co ductors is apair'of c'o'nagfieticnleld which is s ailar to that created by -conductors. The entire assembly is enclosed within a moisture impervious sheath ll of rubher or am; sufllcientlv flexible material or combination of materials which will prevent moisture from entering the interior of the cable.

whfle-rthis description has referred to the con- Figure" 5 .il lll s trates' ia cable wh'lchii s designed I ductors 'aa being; arranged "parallel to each other it will be-understood that this is intended yto cove r a construction in which the conductors and shields are helically arranged to secure greater flexibility. In addition the magnetic field will then covera cylindrical volume of water lnste a't'r 'a' relatively smaller parallelepiped as the'direction the beain'chan'gesradlall along the'le'ngth'oi. th'cablel' 4 In use it' is contemplatedth'at the cable or the present invention wo'uldbe connected with stra p'rovided'with a source-o; electrical energy by a coaxial 6r shielded cable which is inert a's far as the creation cr'a'n xternal'magnetlc field is'bondenied andthe'"go" and mm-h" conductors of the cable are connected together at theif'extreme' ends so asto form's complete electrical 61mg; e a rr in' the'nature or this cable'it will be apparent that in' designing" for 'any'gl'v'en condition it' vluj be necessary first to ascertain the size" of conductors and Shields which will'beneces'sary. and then'to calculate'th -Weighto'ffeah element involved in the construction If'the steclfic gravity of the completed cabl'' de'sign'ed'ln tmsmanner is considerably above that'of water it will be necessary to increase the quantity"of the s' snge rubber qrcther' burlyzirit'fillen'soa to given greate'r'buo ancy to the'cable. Conversely, the thickness bf '15 e layer of sponge rubber may be decreased if the specific gravity isconslderfa'blyl ess than that o'f'water."

It will be obvious from thedescription of the present invention that many changes may be made in the materials of which the conductor or sheath are formed, and that it is to be understood that the device maybe "modified in many ways without departing 'i'romth'e spirit or'the hates-51cm telescope oi thefollowing claims.

substituted for the'spong'e rubbenor'sheathf "What I clalm'is:

' i. Afcable "for the creation or magnetic fields including a'pair' of'parallel conductors and means located betwe n said conductors for beaming the as et o de. in ,7

2. A cable 01. the type described, comprising twocelectric. conductors anrlbeaming means located between thelcondllctors el'feqtiveto distort themagnetimfleli e e a 3. The cable of claim 2 in which the specific gravity ot the cable is less than that of water.

4. An electric cable 01 the'type described-comprising a-pair'of electric conductors'arrangedin parallel relationship and shielding means located between said conductors effective tobeam the magnetic field which results when the-conductors aeve'smeidwarormed ofm'agneticmaterialsuch areenerglzed as a part or the same circuit;-

5. An electric cable comprising a plurality of electric conductors, shielding means located between said conductors effective to beam outwardly from the axis of the cable the magnetic field created by energizing the conductors.

6. The cable of claim 5 in which the conductors and shielding means are helically arranged. '7. The cable 01' claim 5 in which the weight of within a moisture-proof jacket.

EUGENE W. GREENFIELD. 

